Big changes continue for Season 8 of Smallville. The CW has informed The Continuum that Michael Rosenbaum, who played Lex Luthor, is leaving the series as a regular and that next season will include two new villains.

The new villains will be Doomsday from the Superman comic books and "a female antagonist who will challenge Clark in ways never before imagined. "

Casting is underway for both roles.

Here's how the network describes the new villains:

* Doomsday: "In season eight, Clark will face his ultimate challenge with the appearance of the legendary, unstoppable destroyer Doomsday, who appears on Smallville for the first time. As comic book fans know, Doomsday is notorious for being the only character in the DC Comics universe to have killed Superman."

*Female villain: "Doomsday won't be Clark's only nemesis in the upcoming season. The executive producers are tight-lipped about a new female villain they will be introducing, but they can say she will be familiar to many fans and will set her sights on Clark in ways Lex never could. Intelligent, brilliantly manipulative, and dangerously sinister, our gorgeous new villain has one more weapon in her arsenal: Her mutual attraction with Clark may prove to be as deadly as kryptonite for him."

Rosenbaum has been a cast member for all seven seasons of Smallville to date. He was also the voice of Flash in Cartoon Network's Justice League/Justice League Unlimited.

"It has been an honor and pleasure to work with Michael for the past six seasons. He is one of the best actors on television and has never failed to bring a new layer to the character of Lex Luthor in every episode. While Michael won't be a series regular and we won't have the pleasure of working with him on a weekly basis this fall, we like to think that we haven't seen the last of Lex Luthor. Stay tuned."